Process of rendering lithopone more stable against light.



UNITED STATES PATENT OFFICE.

, WILHELM'osTWALn, OF LEIPZIG, GERMANY:

Paoonss on anunname m'rnoronn moan smear: AoAmsr mom.

Specification of Letters Patent.

Patented Earth 23, 1909.

Application filed March 24, 1906. Serial No. 807,796.

To all whom it may concern:

Be it known that I, WILHELM OSTWALD, a

subject of the King of Saxony, residin .at'

2/ 3Li1mstrasse, Leipzig, Kingdom of axony, German Empire, have inventednew and ing mixture of sulfid of zinc and sulfate of barium is thendried, heated, chilled in Water and when finely ground or ulverizedconstitutes the pigment. Besi es very valuable roperties, as itssanitary harmlessness and its stability against the action,of sulfuretedhydrogen, the lithopone has the disadvanta e to be altered by theinfluence of the sun lig t. The pigment becomes gray by the action ofthe sun light.

The object of the present invention is to prevent this alteration and tomanufacture a ithopone more stable against light than the kinds hithertoknown.

I have found that the lithopone will be rendered morestable against liht, if it has been treated with compounds w 'ch have no acid re-actionand. are able to precipitate zinc compounds from solutions of zinccompounds. Compounds of sodium or potassium are especially suitable formy pu ose.

Of the compounds suita le for carrying out my invention the followingmay be men? tioned as examplem-Carbonate of sodium' osphates,pyrophosphates, metaphosphates, borates, cyanids, bicarbon ates,ferrocyanids, sulfids, sulphydrids, hy-" droxids of the alkalies ormixtures of these or potassium, p

com ounds. Also the soluble in water salts of t e earth alkali metalsmay be used. All these compounds may be utilized both separately an alsomixed one with the other.

In order to carry out my invention I can mix the lithopone with thecompounds to be added and use the mixture as a pigment. For instance Imay mix 100 kilograms of dry lithopone with 3 kilograms of d carbonateof sodium or 2.5 kilograms of p osphate of sodium (Na HPO or Na PO,). Ican also use solutionsof the compounds, incorporate the solutions to thelithopone and evaporate the solvent. I may also add the compounds salts,and lixiviating the mixture.

and after a suitable time of action separate the salts bylixiviatingwith water. It is, however,'not advisable toeliminate thetotal quantity of the added salt. I can also incorporatethe same bychilling the'heated mixture of sulfid of zinc and sulfate of barium witha solution of the said compound instead of water alone.

The proportion of the compounds used may be varied. Generally an amount'of l to 3 per cent. of the lithopone will be suitable; I may howeveralso use higher proportions of the compounds, but the quantity of thecom ounds must not be so high that the who e of the zinc sulfid presentin the lithopone is converted into other zinc compounds. One skilled inthe art will find by experimentthe proportions suitable for his specialpurposes. The process may also be used for treating lithopone containingadaixtures such ascalcium compounds or the What I claim and desire tosecure by Letters Patent is -1. The process .of rendering lithopone morestable against light, which consists in adding to lithopone manufacturedin the known manner a metal compound soluble in water withoutdecomposition, having no acid reaction, and being capable ofprecipitaizing zinc compounds from solutions of zinc sa ts. 2. Theprocess of rendering lithopone more stable against light, which consistsin adding to lithopone manufactured in the known manner a metal compoundsoluble in water without decomposition, having no acid reaction, andbeing capable of preclpitating zinc compounds from solutions of zmc 3.The process of rendering lithopone ,more stable against light, whichconsists 1n chilling'the hot lithopone manufactured in the known mannerina solution of a compound having no acid re-action and being able topreclpitate zinc compounds from solutions of zinc salts. v

4. The process of. rendering lithopone more stable against light, whichconsists in adding an alkaline phosphate to lithopone manufactured inthe known manner.

5. The process of rendering lithopone more stable against light, whichconsists in 0 addin an alkaline phosphate to lithopone 6. The process ofrendering lithopone 1 8. As a new'article of manufacture, lithomorestable against light, which consists in pone stableagainst light,containing an alkali chilling the hot lithopone manufactured inphosphate. the known manner in a solution'of an alka- In testimonywhereof I have signed my 1.; line phosphate. name to this specificationin the presence of 7. As 1alnew article plf manufacture, lithoi twosubscribing witnesses. pone sta e against ig t, containing a metacompound soluble in water without decom- WHHELM ObTWALD' position,having no acidreaction, and being capable of precipitating zinccompounds from solutions of zinc salts.

Witnesses:

RUDOLPH FRICKE, SOUTHARD P. WARNER.

